JPH0782312A - Production of polyethylene - Google Patents

Abstract

PURPOSE:To obtain a catalyst system which is so active at temps. higher than the melting point of the polymer that catalyst removal is unnecessary, which is excellent in comonomer reactivity, and with which high-mol.wt. polyethylene can be produced. CONSTITUTION:Polyethylene is produced by polymerizing ethylene alone or copolymerizing ethylene with at least one alpha-olefin using a catalyst system comprising a homogeneous Ti-Mg solution and at least one halogenated organoaluminum compound, the solution being one obtained from (I) metallic magnesium, (II) an oxygenic organic Ti compound, and (III) an alcohol ingredient comprising at least one 6C or higher alcohol in an amount of 1mol per mol of the ingredient (I).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polyethylene using a Ziegler type catalyst having an extremely high activity. More specifically, it relates to a method for producing polyethylene, which comprises homopolymerizing ethylene or copolymerizing ethylene and an α-olefin using a catalyst component having extremely high catalytic activity under a temperature condition of the melting point of the polymer or higher. is there.

[0002]

2. Description of the Related Art Conventionally, as one of the methods for producing an ethylene (co) polymer, a method of polymerizing ethylene in the presence of a so-called Ziegler type catalyst, which is a combination of a transition metal compound and an organometallic compound, or ethylene and α -Methods of copolymerizing with olefins are known. Among them, as a Ziegler type catalyst, it is advantageous to combine a compound of titanium, zirconium or vanadium with an organoaluminum compound in terms of catalytic activity and molecular weight of polyethylene to be obtained, molecular weight distribution, copolymerization composition, etc. Is being used for

When the production methods are classified according to processes, the slurry polymerization method, the gas phase polymerization method, and the polymerization under the temperature conditions above the melting point are carried out under the temperature conditions below the melting point of polyethylene while maintaining the polymer in the particle state. A solution polymerization method and a high temperature high pressure polymerization method are known. Among these polymerization processes, the solution polymerization method and the high-temperature high-pressure polymerization method are effective in terms of energy because the heat of polymerization due to an exothermic reaction can be effectively used. On the other hand, the slurry polymerization method and the gas phase polymerization method, in the low-density polyethylene produced by copolymerization with α-olefin, because the crystallinity of the copolymer is low, it is difficult to keep the copolymer particles in a stable state, Since the reactivity of the higher α-olefin is low, it is difficult to produce a higher α-olefin copolymer having excellent physical properties, which limits the range of products that can be industrially produced. On the other hand, the solution polymerization method and the high-temperature high-pressure polymerization method, by not taking a particle state or by increasing the reactivity of α-olefin by high-temperature reaction,
It is possible to produce high-quality low-density polyethylene in a wide range without the above-mentioned restrictions.

However, since the transition metal compound usually used as a Ziegler catalyst is a solid, it is suspended in an inert solvent. However, when the transition metal compound is continuously supplied to the polymerization reactor, it is precipitated in the transportation pipe. The problem is that it is easy to do and quantitative and constant supply. If it cannot be supplied uniformly, it becomes difficult to carry out the polymerization reaction stably,
As a result, the quality of polyethylene produced will be non-uniform. Therefore, it is necessary to react with α-olefin such as hexene in advance for the purpose of refining the catalyst particles and suppressing sedimentation.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to obtain a comonomer which is highly active in a temperature range higher than the melting point of the polymer, that is, in a solution polymerization method or a high-temperature high-pressure polymerization method, and which has such a high activity that a catalyst removal step is not required. An object of the present invention is to provide a catalyst system which is excellent in reactivity and capable of producing polyethylene having a high molecular weight. Furthermore, it does not require a step of refining the catalyst particles,
It is an object of the present invention to provide a catalyst system capable of stably carrying out a polymerization reaction and thus producing polyethylene of uniform quality.

[0006]

[Means for Solving the Problems] As a result of intensive studies, the present inventors have solved the above problems and developed a highly active polymerization catalyst utilizing the merits of the solution polymerization method and the high temperature and high pressure polymerization method. The inventors have found that the use of a specific transition metal-containing homogeneous solution and a halogen-containing organoaluminum compound exhibits a surprising catalytic activity, and have completed the present invention.

That is, the gist of the present invention is to homopolymerize ethylene or copolymerize ethylene with at least one α-olefin in the presence of a catalyst composed of a transition metal compound and an organometallic compound at a temperature not lower than the melting point of the polymer. In producing polyethylene by the above, (I) metal magnesium and (II) oxygen-containing organic compound of titanium, and (III) titanium-magnesium-containing homogeneous solution ((A) component) and halogen-containing organic compound obtained from alcohol A catalyst system comprising at least one compound selected from aluminum compounds (component (B)) is used, and in the alcohol of component (III), an alcohol having 6 or more carbon atoms is metallic magnesium of component (I). Of polyethylene is characterized by being contained in an amount of 1 mol / mol or more In the production method.

[0008]

The metallic magnesium of the component (I), which is a reactant in the catalyst used in the present invention, can be used in various shapes, such as powder, particles, foil or ribbon.

The oxygen-containing organic compound of titanium used as the component (II) is represented by the general formula [TiO _a (OR ¹ )
A compound represented by _b X ¹ _c ] _n or the like is used. However,
In the general formula, R ¹ represents a hydrocarbon such as an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, a cycloalkyl group, an aryl group, X ¹ represents a halogen atom,
F, Cl, Br or I. a, b and c are a
When ≧ 0, b> 0, and 4> c ≧ 0, the numbers are compatible with the valence of titanium, and n is an integer. Above all, a is 0
It is desirable to use an oxygen-containing organic compound such that ≦ a ≦ 1 and n is 1 ≦ n ≦ 6.

As a concrete example, Ti (OC
_{2 H 5) 4, Ti (} O-n-C 3 H 7) 4, Ti (O-i-C
_{3 H 7) 4, Ti (} O-n-C 4 H 9) 4, Ti 2 O (O-i
_{-C 3 H 7) 6, Ti} (OCH 2 H 5) 2 Cl 2, Ti (OC 2
H _{5) 3} Cl, etc. may be mentioned. Also, (I
Oxygen-containing organic compounds containing several different hydrocarbon groups may be used as component I).

These oxygen-containing organic compounds of titanium are used alone or as a mixture of two or more kinds.

As the alcohol used as the component (III), an alcohol having a hydrocarbon group having 1 to 18 carbon atoms such as an alkyl group and a cycloalkyl group can be used. Examples include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, n-hexanol, 1-ethylhexanol, 2-ethylhexanol, n-octanol, 1-ethyloctanol, n-. Examples include stearyl alcohol, cyclopentanol, cyclohexanol, ethylene glycol and the like.

These alcohols are used alone or as a mixture of two or more kinds. In the present invention, the alcohol used as the component (III) has 6 carbon atoms.
At least one alcohol selected from the above alcohols is 1 m with respect to the metallic magnesium as the component (I).
Must be contained in an amount of ol / mol or more. If this amount is less than that, sufficient activity cannot be obtained, or a uniform titanium-magnesium-containing solution cannot be obtained.

The catalysts (I) (II) used in the present invention
(III) The amount of each component used is not particularly limited,
The molar ratio of magnesium atoms in the component (I) to titanium atoms in the component (II) is 1: 0.01 to 1: 5, preferably 1: 0.02 to 1: 0.5, particularly preferably 1: 0. It is preferable to select the amount to be used so as to be 05 to 1: 0.2. If it deviates from this range, problems such as low polymerization activity and coloring of the product may occur.

As described above, the molar ratio of the magnesium atom in the component (I) to the alcohol having 6 or more carbon atoms contained in the component (III) is 1: 1 or more. And the molar ratio of the whole alcohol used as the component (III) is 1: 2.
It is preferable to select a usage amount of ˜1: 10.

The titanium-magnesium-containing homogeneous solution of the catalyst component (A) is prepared, for example, by (1) suspending the metal magnesium (I) in the oxygen-containing organic compound (II) of titanium, and adding the alcohol (II) thereto.
I) may be added dropwise, and (2) metallic magnesium (I) may be supplied to a solution of titanium-containing oxygen-containing organic compound (II) and alcohol (III).
Is preferred.

In addition, for the purpose of accelerating the reaction, substances capable of reacting with metallic magnesium or forming an addition compound, such as iodine, mercuric chloride, alkyl halides, organic acid esters and organic acids. It is preferable to add a single polar substance or two or more polar substances.

These catalyst preparation reactions can be carried out either in the presence or in the absence of an inert organic solvent, provided that the reactants themselves are not liquid under the operating conditions, or the amount of liquid reactant is If insufficient, it is desirable to carry out in the presence of an inert organic solvent. As the inert organic solvent, all those commonly used in the art can be used, and examples thereof include aliphatic, alicyclic or aromatic hydrocarbons, or halogen derivatives thereof, or a mixture thereof, for example, isobutane, Hexane, heptane, cyclohexane, benzene, toluene, xylene,
Monochlorobenzene and the like are preferably used.

The above-mentioned components (I), (II) and (I
The reaction condition for obtaining a homogeneous solution according to II) is usually -50.
To 300 ° C., preferably 0 to 200 ° C., for 0.5 to 50 hours, preferably 1 to 6 hours in an inert gas atmosphere at normal pressure or under pressure.

The titanium-magnesium-containing homogeneous solution thus obtained may be used as it is, but it is usually diluted with an inert organic solvent and used for the polymerization reaction.

Catalyst component (B) used in the present invention
Are, for example, the general formula AlR ² _m X ² _3-m (wherein R ² represents an alkyl group having 1 to 20 carbon atoms, X ²
Represents a halogen atom, and m is 0 <m <3). Specific examples thereof include diethyl aluminum monochloride, diisobutyl aluminum monochloride, ethyl aluminum sesquichloride, ethyl aluminum dichloride, diethyl aluminum monobromide, diisopropyl aluminum monobromide and the like.

These halogen-containing organoaluminum compounds are used alone or as a mixture of two or more kinds.

The amount of the catalyst component (B) used is such that the molar ratio of halogen atoms to titanium atoms contained in the catalyst is 30 or more and the molar ratio of organic groups to titanium atoms is 30 to 80. It is preferable to select the type and amount used. If it is out of this range, the polymerization activity may be lowered.

The polymerization according to the invention is a homopolymerization of ethylene or a copolymerization of ethylene with at least one α-olefin. The α-olefin used for copolymerization with ethylene is preferably one having 3 to 20 carbon atoms, and specific examples thereof include propylene, 1-butene, 1-pentene, 1-
Hexene, 4-methyl-1-pentene, 1-octene,
1-decene and the like and mixtures thereof are used.

The polymerization of ethylene is carried out at a temperature above the melting point of the produced polymer,
It is preferably carried out in a temperature range of 130 to 300 ° C., and an inert solvent or a monomer itself is used as a polymerization medium.

In solution polymerization using an inert solvent, aliphatic hydrocarbons such as hexane, heptane, octane, nonane, decane, undecane and dodecane and mixtures thereof, aromatic hydrocarbons such as benzene and toluene, Alicyclic hydrocarbons such as cyclohexane and methylcyclohexane are used. Polymerization pressure is 1 to 20
0, preferably 10 to 50 kg / cm ² , and the residence time is in the range of 10 minutes to 6 hours, preferably 20 minutes to 3 hours.

In the high-temperature high-pressure polymerization in which the monomer itself is used as the polymerization medium, a high-pressure radical polymerization device for ethylene can generally be used, and the polymerization pressure is 200 to 25.
00 kg / cm ² , preferably 400-1500 kg /
cm ² , residence time 5 to 600 seconds, preferably 10 to 15
It is performed in the range of 0 seconds.

In the present invention, the molecular weight of the polymer can be controlled by adjusting the reaction temperature, but can be easily controlled by allowing hydrogen to exist in the polymerization zone. The amount of hydrogen varies depending on the polymerization conditions, the molecular weight of the desired ethylene polymer, and the like, so it is necessary to adjust it appropriately.

[0029]

EXAMPLES The present invention will be shown below by examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.

In the examples, MI represents a melt index, which is measured according to JIS K-6760 under the conditions of 190 ° C. and a load of 2.16 kg. The density is
It was measured according to JIS K-6760.

The polymerization activity depends on the amount of titanium 1 in the catalyst component (A).
The amount of polymer produced (g) per gram.

Example 1 (a) [Preparation of catalyst component (A)] 36 g of metal magnesium powder (1.48 m) was placed in a 3 l flask equipped with a stirrer, a reflux condenser, a dropping tube and a thermometer.
ol) and titanium tetrabutoxide 51.6 g (0.
(152 mol), and after adding 1.8 g of iodine, 134.1 g (1.81 mol) of butanol and 231.6 g (1.78 mol) of 2-ethylhexanol,
The temperature was raised to 90 ° C., and the mixture was stirred under a nitrogen blanket for 2 hours while removing generated hydrogen gas. Subsequently, the temperature was raised to 140 ° C and the reaction was continued for 2 hours, and then 2450 ml of heptane
Was added to obtain a catalyst component (A) as a uniform solution containing magnesium and titanium.

The catalyst component (A) thus obtained was added with 10 to 10 carbon atoms.
It was diluted with a solvent containing 11 isoparaffins as a main component (IP-1620 manufactured by Idemitsu Petrochemical Co., Ltd., hereinafter referred to as IP-1620) and used for the following polymerization.

(B) [Ethylene Polymerization] The stainless steel autoclave with an induction stirrer having an internal volume of 2 l was replaced with nitrogen, and 1200 ml of IP-1620 was replaced.
added. Then, ethylaluminum sesquichloride (40 μmol) was added as a catalyst component (B), and the temperature was raised to 200 ° C. with stirring. The inside of the system becomes about 1.0 kg / cm ² G due to the vapor pressure of the solvent, but the total pressure of ethylene is 60.
The catalyst component (A) was added until it reached 0 kg / cm ² G, and 1.0 μmol of the above catalyst component (A) corresponding to titanium atom was added to initiate polymerization. When ethylene was continuously introduced and the polymerization was carried out for 4 minutes while keeping the total pressure constant, 87.6 g of a polymer was obtained. The activity per titanium is 1829 kg /
corresponding to g. The MFR was 0.22 g / 10 minutes.

Examples 2 to 4, Comparative Example 1 Polymerization of ethylene was carried out in the same manner as in Example 1 except that the type and amount of the catalyst component (B) used were as shown in Table 1. The results are also shown in Table 1.

Comparative Example 2 7 g (0.29 mo) of magnesium metal powder was placed in a 1 liter flask equipped with a stirrer, a reflux condenser, a dropping tube and a thermometer.
1) and 39.2 g of titanium tetrabutoxide (0.1
(15 mol), 0.35 g of iodine and 42.9 g (0.58 mol) of butanol were added thereto, and then 90 ° C.
The temperature was raised to, and the mixture was stirred for 2 hours under a nitrogen blanket while removing the generated hydrogen gas. Subsequently, the temperature was raised to 140 ° C. and the reaction was carried out for 2 hours, and then 815 ml of heptane was added to obtain a catalyst component of a homogeneous solution containing magnesium and titanium.

The obtained catalyst component was diluted with IP-1620 and used in the following polymerization.

Ethylene was polymerized under the same conditions as in Example 1 using the above catalyst component and ethylaluminum sesquichloride. The results are shown in Table 1, but the activity was insufficient.

[0039]

[Table 1]

Comparative Example 3 A stainless steel autoclave with an induction stirrer having an internal volume of 2 liters was purged with nitrogen to obtain 1200 ml of IP-1620.
added. Then, ethylaluminum sesquichloride (40 μmol) was added as a catalyst component (B), and the temperature was raised to 200 ° C. with stirring. The inside of the system becomes about 1.0 kg / cm ² G due to the vapor pressure of the solvent, but the total pressure of ethylene is 60.
It is filled up to 0 kg / cm ² G and a heptane solution of titanium tetrabutoxide is 1.0 μm equivalent to titanium atom.
was added to initiate polymerization. Polymerization was carried out for 4 minutes while continuously introducing ethylene and keeping the total pressure constant, but the activity was very low at 8.5 kg / g-Ti.

Example 5 In a vertical cylindrical reactor equipped with a stirrer, the catalyst component (A) of the homogeneous solution obtained in Example 1 and ethylaluminum sesquichloride as the catalyst component (B) were used, and ethylene, 1-
Hexene and hydrogen were continuously supplied to carry out the polymerization while maintaining the temperature in the polymerization vessel at 180 ° C. and the pressure at 800 kg / cm ² G. The average residence time in the polymerization vessel was 50 seconds, the molar ratio of ethylene and 1-hexene was 65/35, and hydrogen was 3
0 l / hr, the catalyst supply was such that the catalyst component (A) was titanium equivalent to 0.25 mmol / hr, and ethyl aluminum sesquichloride was 10.2 mmol / h as the catalyst component (B).
It was supplied at r and polymerization was carried out for 8 hours. As a result, 20.0 kg of ethylene copolymer was obtained per hour. The polymerization activity of the catalyst component (A) per titanium was 1670 k.
Corresponding to g / g. MI is 2.4 g / 10 minutes,
The melting point of the polymer is 123 ° C. and the density is 0.923 g / cm ^3.
Met.

Examples 6 to 7 Copolymerization of ethylene and 1-hexene was carried out in the same manner as in Example 5 except that the polymerization conditions were as shown in Table 2. The results of the polymerization are shown in Table 3.

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

The effect of the present invention is that, firstly, a polymer having extremely high polymerization activity per transition metal and not requiring a deashing step for the purpose of catalyst removal can be obtained. Since it is highly active, there is no need to worry about product coloring or odor, and polymer purification is not required, which is extremely economical.

The second effect of the present invention is that the thermal stability of the catalyst is excellent. Therefore, the active life is relatively long even at high temperatures.

The third effect of the present invention is that the molecular weight of the obtained copolymer can be increased. Therefore, for hollow molding,
A (co) polymer suitable for film molding can be obtained, and the surface properties of the molded product are improved.

The fourth effect of the present invention is that it has good copolymerizability with other α-olefins (comonomer).
Polymerization conversion of comonomer is higher than other catalyst systems (the amount of α-olefin to be copolymerized is small).

The fifth effect of the present invention is that since both the component (A) and the component (B) are liquid, it is easy to constantly supply them to the polymerization reactor and the polymerization reaction is carried out stably. As a result, polyethylene of uniform quality can be obtained.

[Brief description of drawings]

FIG. 1 is a catalyst preparation diagram (flow chart) in the present invention.
Indicates.

Claims (1)

[Claims] 1. In the presence of a catalyst composed of a transition metal compound and an organic metal compound, ethylene is homopolymerized with ethylene at a reaction temperature not lower than the melting point of the polymer or ethylene and at least one α-type compound.
In producing polyethylene by copolymerizing olefins, (I) metal magnesium and (II) an oxygen-containing organic compound of titanium, and (II)
I) A catalyst system comprising a titanium-magnesium-containing homogeneous solution (component (A)) obtained from an alcohol and at least one compound (component (B)) selected from halogen-containing organoaluminum compounds is used. In the alcohol of the component (III), the alcohol having 6 or more carbon atoms is 1 with respect to the metallic magnesium of the component (I).
A method for producing polyethylene, characterized in that it is contained in an amount of mol / mol or more.